1. Field of the Invention
The present invention relates to a portable terminal device having a position acquisition function and a navigation (guiding) function, a system including the portable terminal device, and a recording medium storing a program which allows a computer to function as the foregoing portable terminal device.
2. Description of the Related Art
A mobile phone device which has a GPS (Global Positioning System) function and a navigation function, and navigates a route to a destination based on a present position, is known. Unexamined Japanese Patent Application KOKAI Publication No. 2004-294429, for example, discloses such a mobile phone device which has a navigation function for navigating a route to a destination where a user should return, such as a home.
In general, navigation function is highly burdened, and consumes a large electrical power. On the other hand, mobile phones are generally operated by a battery in view of portability. Therefore, if the navigation function is continuously activated, a problem such as battery run-out may occur easily. Thus, the mobile phone disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2004-294429 activates the navigation function only when a user instructs to operate.
For example, in the case of a group bus tour, the location where people got off is often appointed as the position-to-return where the people get back after off-the-bus free sightseeing. In this case, it is difficult for people to determine timing to start returning to the position-to-return, and a navigation function is useful for guiding the route to the position-to-return. However, if the navigation function is activated before it is necessary, the battery may run out while returning.
Not only in the case of a bus tour but also a case of meeting a person, similarly to the case of off-the-bus sightseeing, the navigation function may be activated often before it is necessary, the battery may also run out on the way.
Also, an operation for setting the navigation function is troublesome and confusing, and there is a problem that children and old people cannot be friendly with operation and fully utilize the navigation function. Even if the child carries a mobile phone with the navigation function, there is a case that the child cannot use the mobile phone with the navigation function when he gets lost from his parents.